Repairing dented fo...
 

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Repairing dented fork lowers- exhaust pipe expander

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Anyone tried this!?

My yaris have a dent about 5cm from the bottom of the leg

Found a thread on mtbr saying its possible but no examples


 
Posted : 29/05/2021 11:24 am
 poah
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buy new lowers


 
Posted : 29/05/2021 12:18 pm
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How deep is the dent and does it interfer with the action of the fork?


 
Posted : 29/05/2021 12:30 pm
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poah
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buy new lowers

Even better would be a second hand set of Yaris (£200 for good ones when I last look, obvs add COVID tax now) and keep all the other parts as spares


 
Posted : 29/05/2021 1:55 pm
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Yeah 2nd hand Yaris are £250+ or new lowers which are £250!

Its not urgent, been sitting in my garage for a year, just wondered if I could fix them

They stop the last few cm of travel, looking inside the bushings are a few mm proud of the tube, so I just need to get them straight enough for the stanchion to clear

I've ordered the expander anyway

https://flic.kr/p/2m2oF59


 
Posted : 29/05/2021 3:07 pm
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Cast aluminium/magnesium alloy is not something I would be trying to bend back.


 
Posted : 29/05/2021 3:37 pm
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True, but there's nothing to lose.


 
Posted : 29/05/2021 3:45 pm
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I’d not be using that again.


 
Posted : 29/05/2021 4:15 pm
 5lab
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I've got some old domain lowers kicking about if they're the same?


 
Posted : 29/05/2021 5:17 pm
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Cheers, 5lab!, I think theyre probably different

I'll try and fix them

Either they crack when I'm fixing

Or
I fix it and they explode on the first drop/jump/turn

Or
I'm a mechanical god and it all works out fine


 
Posted : 29/05/2021 5:30 pm
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Can't you find a set of forks with the stantions scratched that are selling cheap?

My sure you take some life insurance out and take lots of pictures for our amusement 😂

Good luck


 
Posted : 29/05/2021 6:00 pm
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Will it go deep enough down the leg? I thought they were quite short and you still needed to be able to hold the end of it to grip while tightening?


 
Posted : 29/05/2021 6:27 pm
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Nothing to lose ?, ask Doddy on gmbn about fork failure.😀


 
Posted : 29/05/2021 6:32 pm
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I've blown out dozens of exhausts with varying degrees of success and I can't see this working. Just intuition, no scientific grounds for this. A thin steel exhaust can take about 30psi to move and I'd be amazed if you could get enough pressure in the lower to do it but I'm fascinated to see what happens. Los of PPE please, the aluminium might give way altogether rather than move in a controlled fashion.
I've straightened wheel rims (off-road ones) with heat and a vice and not had a failure in use but aluminium is not very predictable as far as failure goes so be careful.


 
Posted : 29/05/2021 8:00 pm
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Can you splint the fork leg with some steel tube cut in half lengthways and jubilee clipped on? Then the expander tool won't go too far (hopefully).


 
Posted : 29/05/2021 11:46 pm
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I hope you know a good dentist.


 
Posted : 30/05/2021 6:52 am
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Not mine and no connection but could be helpful.

https://www.ebay.co.uk/itm/Mountain-Bike-Forks-Spares-Or-Repairs-/174780454125?_trksid=p2349624.m46890.l49286


 
Posted : 30/05/2021 3:10 pm
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That eBay. How do you break a stanchion like that? No obvious damage anywhere else (only had a cursory glance)


 
Posted : 30/05/2021 5:08 pm
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That is impressive, I'm guessing fat person with very high air pressure + not enough rebound damping causing very harsh top out force onto the O-ring.


 
Posted : 30/05/2021 5:29 pm
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Thanks clubby, I'm watching that, ime it'll go for quite a bit, CSUs come up up on ebay now & again, but lowers are much rarer


 
Posted : 30/05/2021 5:46 pm
 tish
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Are they boost or non boost?
I’m sure I’ve got a set of non boost Lyrik lowers in the garage if they are any good to you.


 
Posted : 30/05/2021 6:11 pm
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Cheers tish, that's v generous, they are boost tho


 
Posted : 30/05/2021 6:15 pm
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27.5 or 29


 
Posted : 30/05/2021 7:23 pm
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29 endomick but....

Expander arrived today

(For extra bodge, Didn't have a long enough socket extender, couldn't wait to get one tomorrow, so I rammed a chisel into the extender and turned it with some molgrips)

https://flic.kr/p/2m2NR35

So it seems to have pushed it out enough

https://flic.kr/p/2m2J78K

Stanchions run smoothly with no interference (there's still a small dent inside, I suppose it could be an issue under load) I'll try and get out for a test ride this week


 
Posted : 31/05/2021 9:14 pm
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A car exhaust is not a structural load bearing item. By denting your fork, you've taken that bit of metal past its yield point. Expanding it back will further weaken it. I really wouldn't ride that fork if I was you.


 
Posted : 31/05/2021 9:54 pm
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there’s still a small dent inside, I suppose it could be an issue under load)

Can see why that would happen, common to have to push past where you need it as it’ll spring back slightly when you remove the press. However, if it’s clear then have a go. I’d not be overly concerned about riding it if it was mine, seen far scarier things being bent/push/pulled into shape in work!


 
Posted : 31/05/2021 10:48 pm
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I'd agree mashr, keep an eye on it for any signs of cracking, there's very little chance of it failing catastrophically.


 
Posted : 31/05/2021 10:54 pm
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How did you get the bottom to not turn so you could tighten in with your chisel?  Was it just an interference got and that was enough?


 
Posted : 01/06/2021 1:53 am
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A car exhaust is not a structural load bearing item. By denting your fork, you’ve taken that bit of metal past its yield point. Expanding it back will further weaken it.

Without any material test data, we can't say that for sure. If it's pushed back out without any signs of cracking, it's probably fairly ductile. I'd ride it.


 
Posted : 01/06/2021 6:24 am
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Excellent work. 💪


 
Posted : 01/06/2021 8:12 am
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Was it just an interference got and that was enough?

I lined it up outside so I knew what depth my chisel handle had to be and had it wide enough so it just caught on the sides with a bit of wiggling


 
Posted : 01/06/2021 8:33 am
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First ride on them today,

I didn't die

Tried to hit as many drops as possible and left compression off so they'd sit low in travel

All seemed fine, I'll take the lowers off and see if the stanchions have any marks, but I didn't feel any binding or hear any clunks


 
Posted : 11/06/2021 2:10 pm
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Very cool.


 
Posted : 11/06/2021 3:03 pm
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That was completely on my 'no way that can work' list so thank you, I've learned something.  It's also something I think I would only risk on my own bike


 
Posted : 11/06/2021 4:04 pm
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It’s also something I think I would only risk on my own bike

How different people are, I'd absolutely only risk that on someone else's bike.


 
Posted : 11/06/2021 4:36 pm
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First ride on them today,

I didn’t die

Lies. You're clearly posting from beyond the grave. Top bodging. Personally though you're braver than me. A new pair of lowers is a lot cheaper than a new pair of teeth!


 
Posted : 11/06/2021 5:52 pm
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Super job, in flip flops too.


 
Posted : 12/06/2021 7:21 am
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A new pair of lowers is a lot cheaper than a new pair of teeth!

Given these didn't crack when he opened out the dent .

I'm struggling to see a situation where these go from zero to hero in 2 seconds and deposit him on his face unless he gets something really wrong and/or goes blind and deaf


 
Posted : 12/06/2021 8:04 am
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@kimbers
I'm in the exact situation as you were here—old fork sitting in my garage with a minor dent...I started digging the interwebs and found this old thread. Are you still running this fork? Where did you get your expander tool? I'm hoping to repair my fork so I can throw it on a cheap hardtail build...not a heavy use bike.


 
Posted : 28/04/2022 9:12 pm
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Heya

Yep running fine, including ews tweedlove since then, so seems alright

Where are you based you can use my expander, if near


 
Posted : 28/04/2022 9:17 pm
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Nice one, I'd ride them. Even if they were to crack, I cant see them exploding catastrophically.

Double points for the safety sandals too 😉


 
Posted : 29/04/2022 8:53 am
 rsl1
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Are you still checking them for cracks regularly? I'm honestly surprised they've gone 10 months without issue. No one in the original response went into the detail but by denting them and then also bending back, you have work hardened the metal. This actually makes it stronger, but with the big disadvantage (when done unintentionally rather than by design) that it makes it more brittle and prone to fatigue cracking and failure. I would strongly recommend regular checks for cracks and personally wouldn't ride them myself. Even wikipedia agrees "Aluminum
Devices made from aluminum and its alloys, such as aircraft, must be carefully designed to minimize or evenly distribute flexure, which can lead to work hardening and, in turn, stress cracking, possibly causing catastrophic failure."

My vote would be to turn them into a lamp and get some replacement lowers to actually ride on...


 
Posted : 29/04/2022 9:22 am
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Whereas in the real world, he's been riding and racing on them for almost a year.

Good work Kimbers. Waste not want not.


 
Posted : 29/04/2022 9:26 am
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I'd have no worries riding them.
Looks like its in a pretty low stress area.
Near the axle or on the front where the ridge starts for the brace and I'd me more worried.
If it does start to crack you'll soon see as the air pressure on full compression will push oil out and make it obvious.


 
Posted : 29/04/2022 9:35 am
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I'm in northern Utah...it looks like Harbor Freight has one for $19.99...I'll just order one of those or talk to an autobody friend of mine.
Thanks for guinea pigging this problem!


 
Posted : 02/05/2022 4:24 pm
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@shkoogy did you have a go?


 
Posted : 19/05/2022 10:49 pm
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Unfortunately no. I still need to order the tool. I’ll post here after I do it though


 
Posted : 20/05/2022 3:23 pm
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Thanks kimbers for sharing this.
Got pretty much the same thing happening to me.
Expander arrives tomorrow together with a Heat Gun. Was wondering if it would be better to heat that up before using the expander? might make it more easy to fix?
https://flic.kr/p/2nyXmN9
https://flic.kr/p/2nyURxq


 
Posted : 18/07/2022 3:39 pm

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